From herron at ELLINGTON.com  Fri Jan 26 16:20:31 2018
From: herron at ELLINGTON.com (Liam Herron)
Date: Fri, 26 Jan 2018 21:20:31 +0000
Subject: [C++-sig] How can I get access to "argv/argc" command line in a
 boost python c++ extension?
Message-ID: <96426055F003C542B3FB8A0928736DF9031D336907@EX2.ELLINGTON.com>

So I have a boost python extension C++ library.  I would like to access the "python commandline" in C++ without having to pass in the "sys.argv" into my C++ extension.
Is there a way to do this?   Include some boost python header and read it from some init variables or something?

e.g.
python  someScript.py  A B C 1 2 3

//////////////////////////////////////////////////////////////////////////

class_<DummyCppClass>
      ("DummyCppClass", "DummyCppClass obj", init<>())
      .def("printCmdLine", &DummyCppClass::printCmdLine)
     ;

//////////////////////////////////////////////////////////////////////////

#include <string>
#include <iostream>

std::string DummyCppClass::printCmdLine() const
{
    std::cout <<   "Prog: " << HERE_argv[0] << ", Arg1: " << HERE_argv[1] << std::endl;
}

//////////////////////////////////////////////////////////////////////////







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From stefan at seefeld.name  Fri Jan 26 17:47:23 2018
From: stefan at seefeld.name (Stefan Seefeld)
Date: Fri, 26 Jan 2018 17:47:23 -0500
Subject: [C++-sig] How can I get access to "argv/argc" command line in a
 boost python c++ extension?
In-Reply-To: <96426055F003C542B3FB8A0928736DF9031D336907@EX2.ELLINGTON.com>
References: <96426055F003C542B3FB8A0928736DF9031D336907@EX2.ELLINGTON.com>
Message-ID: <72d6f314-5d63-1c09-e66b-ef35549dc0af@seefeld.name>

On 26.01.2018 16:20, Liam Herron wrote:
>
> So I have a boost python extension C++ library.? I would like to
> access the ?python commandline? in C++ without having to pass in the
> ?sys.argv? into my C++ extension.???
>
> Is there a way to do this??? Include some boost python header and read
> it from some init variables or something?
>

You don't have to pass `sys.argv` as an argument. You can inspect it
from wherever you need it. Just import `sys` and inspect the elements of
`sys.argv`, just as you would do in Python.


Stefan

-- 

      ...ich hab' noch einen Koffer in Berlin...
    

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From charlie at charliedyson.net  Fri Jan 26 10:27:34 2018
From: charlie at charliedyson.net (Charlie Dyson)
Date: Fri, 26 Jan 2018 15:27:34 +0000
Subject: [C++-sig] Boost-Python: Inconsistent shared_ptr use-count since
 Boost 1.63
Message-ID: <CABYr9QsuxTkeupHMCQMPDofNwkzybgvbJvy5bgYiC_BXKT8bWQ@mail.gmail.com>

I believe the following behaviour changes in 1.63 judging by the
ChangeLog, though unfortunately I can only test 1.60 vs 1.66 at the
moment. Using Enterprise Linux 7 with gcc 7.2.

Consider this module:

#include <boost/python.hpp>
#include <iostream>
#include <memory>

namespace bp = boost::python;

struct X
{
  ~X () { std::cout << "Bye bye" << std::endl; }
};

BOOST_PYTHON_MODULE (pymodule)
{
  bp::class_<X, std::shared_ptr<X>> x_wrap ("X");

  // Not needed in newer boost
  bp::register_ptr_to_python<std::shared_ptr<X>> ();

  auto x1 = std::make_shared<X> ();
  auto x2 = bp::extract<std::shared_ptr<X>> (bp::object (x1)) ();

  // On a newer boost: use counts are not the same
  std::cout << x1.get () << ": "<< x1.use_count () << std::endl; // 2
  std::cout << x2.get () << ": "<< x2.use_count () << std::endl; // 1 :(
}

For the older Boost, the reference counts are both two, but they are 2
and 1 respectively in the newer Boost. Is this expected? I wonder if
there's some cleverness involving x2 somehow pointing to a BP object
that in turn points to x1. Curiously X appears to only be destructed
once, so it doesn't look like UB.

Where it bites me is cleanup time. If I add the following to the end
of the module, I get a segfault:

  static std::vector<std::shared_ptr<X>> v {x2};

Backtrace as follows:
#0  subtype_dealloc (self=0x7ffff7e24050) at Objects/typeobject.c:955
#1  0x00007fffef9dfb59 in xdecref<_object> (p=<optimized out>) at
./boost/python/refcount.hpp:38
#2  reset (this=0x6c1f30) at ./boost/python/handle.hpp:222
#3  boost::python::converter::shared_ptr_deleter::operator()
(this=0x6c1f30) at libs/python/src/converter/builtin_converters.cpp:35
#4  0x00007ffff7ff563a in _M_release (this=0x6c1f20) at
.../bits/shared_ptr_base.h:154
#5  ~__shared_count (this=<optimized out>, __in_chrg=<optimized out>)
    at .../bits/shared_ptr_base.h:684
#6  ~__shared_ptr (this=<optimized out>, __in_chrg=<optimized out>)
    at .../bits/shared_ptr_base.h:1123
#7  ~shared_ptr (this=<optimized out>, __in_chrg=<optimized out>) at
.../bits/shared_ptr.h:93
#8  _Destroy<std::shared_ptr<X> > (__pointer=<optimized out>) at
.../bits/stl_construct.h:98
#9  __destroy<std::shared_ptr<X>*> (__last=<optimized out>, __first=0x678920)
    at .../bits/stl_construct.h:108
#10 _Destroy<std::shared_ptr<X>*> (__last=<optimized out>,
__first=<optimized out>)
    at .../bits/stl_construct.h:137
#11 _Destroy<std::shared_ptr<X>*, std::shared_ptr<X> >
(__last=0x678930, __first=<optimized out>)
    at .../bits/stl_construct.h:206
#12 std::vector<std::shared_ptr<X>, std::allocator<std::shared_ptr<X>
> >::~vector (this=0x7ffff7ff7a60 <init_module_pymodule()::v>,
    __in_chrg=<optimized out>) at .../bits/stl_vector.h:434
#13 0x00007ffff6d24e69 in __run_exit_handlers () from /lib64/libc.so.6
#14 0x00007ffff6d24eb5 in exit () from /lib64/libc.so.6
#15 0x00007ffff6d0db1c in __libc_start_main () from /lib64/libc.so.6
#16 0x00000000004007a1 in _start ()

Is this a new behaviour change, or a bug, or was it always dangerous
and I have just been lucky until now?

Many thanks,

Charlie

From apap at coventor.com  Mon Jan 29 09:53:57 2018
From: apap at coventor.com (apap at coventor.com)
Date: Mon, 29 Jan 2018 14:53:57 +0000
Subject: [C++-sig] How can I get access to "argv/argc" command line in a
 boost python c++ extension?
In-Reply-To: <72d6f314-5d63-1c09-e66b-ef35549dc0af@seefeld.name>
References: <96426055F003C542B3FB8A0928736DF9031D336907@EX2.ELLINGTON.com>
 <72d6f314-5d63-1c09-e66b-ef35549dc0af@seefeld.name>
Message-ID: <SN1PR01MB1936CCAE27A8330BB2DA47C7ADE50@SN1PR01MB1936.prod.exchangelabs.com>

unsubscribe

From: Cplusplus-sig [mailto:cplusplus-sig-bounces+andras.pap=coventor.com at python.org] On Behalf Of Stefan Seefeld
Sent: Friday, January 26, 2018 5:47 PM
To: cplusplus-sig at python.org
Subject: Re: [C++-sig] How can I get access to "argv/argc" command line in a boost python c++ extension?

On 26.01.2018 16:20, Liam Herron wrote:
So I have a boost python extension C++ library.  I would like to access the "python commandline" in C++ without having to pass in the "sys.argv" into my C++ extension.
Is there a way to do this?   Include some boost python header and read it from some init variables or something?

You don't have to pass `sys.argv` as an argument. You can inspect it from wherever you need it. Just import `sys` and inspect the elements of `sys.argv`, just as you would do in Python.

[Stefan]

--



      ...ich hab' noch einen Koffer in Berlin...


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From mohan.varma at gmail.com  Wed Jan 31 10:07:03 2018
From: mohan.varma at gmail.com (Mohan Varma)
Date: Wed, 31 Jan 2018 20:37:03 +0530
Subject: [C++-sig] Copying string values to ndarray using Boost.Python
Message-ID: <CAKr=Qrr=gMBjDa+1jWkddeH+x_qi_TJFUTuzEmoFup=t4bG+hw@mail.gmail.com>

I have been trying to create an ndarray in C++ using Boost.Python while
creating a Python module. The ndarray object is created using a composite
dtype with an int value column, a 32-byte string column and a float value
column. I am able to set the values for int and float columns and access
them in Python. I am not sure on how to set the string column values in
C++. Here is the synopsis of my code, I believe it explains the problem
fairly well. Any help in this regard is greatly appreciated.

struct Test
{
    int id;
    std::string name;
    float value;
};

std::vector<Test> test_values;

//
namespace bp = boost::python;
namespace np = boost::python::numpy;
//

//
bp::tuple shape = bp::make_tuple(test_values.size());

bp::list list_for_dtype;
list_for_dtype.append(bp::make_tuple("id",np::dtype::get_builtin<int>()));
list_for_dtype.append(bp::make_tuple("name", np::dtype(bp::str("U32"))));
list_for_dtype.append(bp::make_tuple("value",np::dtype::get_builtin<float>()));

np::dtype custom_dtype = np::dtype(list_for_dtype);
int item_size = custom_dtype.get_itemsize();
np::ndarray values_array = np::zeros(shape, custom_dtype);

char * dest_ptr = (char *) values_array .get_data();
for (size_t i = 0; i < test_values.size(); ++i) {
    memcpy((void *) dest_ptr, &test_values[i].id, sizeof(int));
    dest_ptr += sizeof(int);

    // How do I copy the string value to ndarray buffer?
    //bp::str bpname(&test_values[i].name);
    //memcpy((void *) dest_ptr, bpname.ptr(), sizeof(float));
    dest_ptr += 32 * 4;

    memcpy((void *) dest_ptr, &test_values[i].value, sizeof(float));
    dest_ptr += sizeof(float);
}

Thank you,
Mohan.
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